Methods and systems for an actuation system

ABSTRACT

Methods and systems are provided for an actuation system for a parking mechanism in a transmission system of a vehicle. In one example, a system may include an actuator coupled to a lever arm via one or more parallel axis gears, and a shaft connecting the lever arm to a pawl of the parking mechanism, the lever arm non-back drivable at each of a first state and a second state of the actuation system.

TECHNICAL FIELD

The present description relates generally to methods and systems for anon-back drivable actuation system for a parking mechanism of a vehicletransmission system (or electric axle system).

BACKGROUND AND SUMMARY

Motorized vehicles may include a shift-by-wire system electricallycoupling an automatic transmission of the vehicle to an instrument panelwithin a cabin of the vehicle. A user may interact with the instrumentpanel in order to select a gear mode of the transmission such as drive,park, neutral, etc. Upon the user selecting park as the desiredtransmission mode, a parking pawl may be actuated to engage a park gearof the transmission system and lock rotation of the park gear, therebypreventing the vehicle from moving. The park gear may be unlocked bydisengaging the park gear from the park pawl.

Once the park gear is locked, the transmission system is desired to beheld in the park mode until it is indicated by the user via theinstrument panel to shift to a different gear mode. Also, upondisengagement and during vehicle travel, it is desired to maintain thepark gear in the disengaged state. In the actuation system of the pawl,a very small rotational actuation of a lever may be desired to shift anoutput shaft of the actuator to an engaged/disengaged state(corresponding to an engaged/disengaged state of the pawl), along with adesired high rate of speed and accuracy. Once engaged/disengaged, theoutput shaft is desired to be non-back drivable to maintain the positionof the pawl. Approaches for attaining the desired non-back drivableactuation mechanism for the pawl may include use of worm gears. However,the inventors herein have recognized potential issues with such systems.Use of worm gears that are non-back drivable exhibit an efficiency oflower than 50% which may result in significant loss of efficiency andcosts. Further, systems involving extended use of a motor may increasepower consumption and costs associated with the operation.

In one example, the issues described above may be addressed by anactuation system in a parking mechanism of a vehicle, comprising: anactuator coupled to a lever arm via one or more gears, and a shaftconnecting the lever arm to a shifting member of the parking mechanism,the lever arm non-back drivable at each of a first state and a secondstate of the actuation system. In this way, by using a parallel axisgear train to actuate a pawl of a parking mechanism, a non-back drivableactuation system may be attained where a small movement of a motor maysuffice to transition the parking mechanism from a disengaged positionto an engaged position.

As one example, a parking mechanism of a vehicle transmission system mayinclude a pawl that is selectively engaged to a parking gear uponselection of park (by a user) as the desired transmission system mode.The parking mechanism may be actuated between a first state where thepawl is engaged to the parking gear to inhibit further movement of thevehicle wheel and a second state where the pawl is disengaged from theparking gear allowing transmission system to rotate the wheels. Anelectronic actuation system may include a motor connected via a drivemechanism such as a parallel axis gear train, the drive mechanismincluding an output shaft coupled to a parallel axes gear system. Theoutput shaft may be mounted on a lever arm and the lever arm may bemounted on a drive pin housed within a slot. The drive pin may becoupled to a final gear of the gear train to drive the lever arm, thedrive pin being eccentric to the final gear to generate a cam effect. Alocking pin may be coupled to the final gear to inhibit further motionof the lever arm upon reaching one of the first state and the secondstate and lock the parking mechanism in the desired engaged/disengagedstate. The output shaft may be coupled to the pawl via a cam. In orderto engage the pawl, the final gear may be rotated in a counterclockwisedirection past a tangent point where the direction of travel of thedrive pin is tangent to the axis of the lever until the lever is locked(first locked position) at the locking pin. In order to disengage thepawl, the final gear may be rotated in a clockwise direction past thetangent point until the lever is locked (second locked position) at thelocking pin and corresponding rotation of the cam disengages the pawlfrom the parking gear. At the locked positions, the lever may not beback-drivable. In the first locked position, the output shaft of thelever arm may cause the cam to rotate and engage the pawl with theparking gear while in the second locked position the output shaft of thelever arm may cause the cam to rotate and disengage the pawl with theparking gear.

In this way, by including a drive pin eccentric to a final gear of aparallel axis gear train and a locking pin on the final gear, a levercoupled to the parallel axis gear train may be locked in one of twodistinct positions. By locking the lever in one of a first and a secondposition, it is possible to maintain the pawl of the parking mechanismat a desired engaged or disengaged position. The technical effect ofusing the actuation system with the parallel axis is that due to thenon-back drivable feature of the actuation system, when the park mode ofthe transmission system is selected, the wheels may not move and vehiclemay not slide, and when the transmission mode is changed from park, thepawl may not be unintentionally engaged when the vehicle is beingdriven. Overall, the actuation system includes a simplified arrangementof components that may be used in a cost-effective manner for engagementand disengagement of the parking mechanism.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows an example parking mechanism of a transmission systemincluding an electronic actuation system.

FIG. 2A shows a schematic of the electronic actuation system of FIG. 1in a first state.

FIG. 2B shows a schematic of the electronic actuation system of FIG. 2Atransitioning from the first state to a second state.

FIG. 2C shows a schematic of the electronic actuation system of FIG. 2Ain the second state.

FIG. 3A shows a first position of the parking mechanism of thetransmission system.

FIG. 3B shows a second position of the parking mechanism of thetransmission system.

FIG. 4 shows a flow-chart illustrating an example method for operatingthe electronic actuation system of the parking mechanism.

DETAILED DESCRIPTION

The following description relates to systems and methods for a non-backdrivable electronic actuation system for a parking mechanism of avehicle transmission system. The parking mechanism may be actuatedbetween a first state and a second state via the electronic actuationsystem is schematically shown in FIG. 1. The first state of the parkingmechanism, as shown in FIG. 3A, may correspond to a park mode of thetransmission system, as selected by a user and the second state of theparking mechanism, as shown in FIG. 3B, may correspond to any mode ofthe transmission system expect the park mode. The electronic actuationsystem including a parallel axis gear train is shown in FIGS. 2A-C. Theparking mechanism may be engaged corresponding to a first state of theelectronic actuation system, as shown in FIG. 2A, or disengagedcorresponding to a second state of the electronic actuation system, asshown in FIG. 2C. Transitioning of the electronic actuation system fromthe first state to the second state is shown in FIG. 2B. A vehiclecontroller may carry out a control routine, such as via the controlroutine of FIG. 4 to operate the electronic actuation system based on amode of the transmission system as selected by the user.

FIG. 1 shows an example 100 of a parking mechanism 101 of a transmissionsystem including an electronic actuation system 201. The parkingmechanism 101 may include a parking gear 115 of the transmission system,the parking gear including alternating teeth 118 and ridges 116. Theparking gear 115 may be coupled to an output shaft of the transmissionsystem and may rotate with rotation of the output shaft.

A spring loaded pawl 110 may be positioned proximal to the parking gearand pivotally connected to a casing of the transmission system via thepivot 113. The pawl 110 may include an elongated portion ending in aprotruded tooth 114. The pawl 110 may be moved upwards and downwardsabout the pivot 113. The end of the tooth 114 may be sized to occupy aridge 116 between consecutive teeth 118 of the parking gear 115. Thetooth 114 of the pawl 110 may include an arcuate upper surface and aroller 112 may be housed within the arcuate top portion of the pawltooth 112. The roller 112 may be rotatable about its central axis, aboutthe point 122.

The roller 112 may be in face sharing contact with a lobe of a cam 108.Rotation of the cam 108 may translate into rotation of the roller 112.The cam 108 may include a higher diameter surface 109 which may comeinto contact with the roller 112 upon rotation of the cam 108. Theelectronic actuation system 201 may be coupled to the cam via a shaft104 and one or more flanges 106.

The electronic actuation system 201 may include the one or more parallelaxis gears such as a first parallel axis gear, a second parallel axisgear, and a final parallel axis gear coupled to a first end of a leverarm 218 via an eccentric drive pin. An output shaft 224 may be coupledto a second end of the lever arm 218 distal from the first end. Anactuator 202 such as an electric motor may be coupled to the firstparallel axis gear to rotate the one or more parallel axis gears. Theelectronic actuation system 201 may be maintained in a first state or asecond state. As an example, the lever arm 218 coupled to the actuator202 via the parallel axis gear train may be rotated in a first directionuntil an output gear of the parallel axis gear train is driven past atangent point and is non-back drivable from the first state of theactuation system. In another example, the level arm may be rotated in asecond direction until the output gear is driven past the tangent pointand is non-back drivable from a second state of the actuation system,the second direction opposite to the first direction. Details of theelectronic actuation system 201 is described in relation to FIGS. 2A-2C.

In the first state of the electronic actuation system 201, as shown inexample 300 in FIG. 3A, the parking mechanism 101 may be actuated to afirst position corresponding to a park mode of the transmission systemas selected by the user. In the first state, rotation of the outputshaft 224 causes the cam 108 to rotate and the higher diameter surface109 to come in contact with the roller 112. The higher diameter surface109 of the cam 108 causes the roller 112 to push down the teeth 114 ofthe pawl 110 into a ridge 116 between two teeth 118 of the parking gear115. By lodging the teeth 114 of the pawl 110 within the ridge 116, theparking gear 115 is locked in a position. Due to the parking gear 115being locked (stopped from moving), the output shaft of the transmissionsystem may no longer cause the vehicle wheels to rotate, therebyaverting further motion of the wheels. In the second state of theelectronic actuation system 201, as shown in example 350 in FIG. 3B, theparking mechanism may be actuated to a second position corresponding toa mode of the transmission system other than the park mode (such asdrive, reverse, etc.) as selected by the user. In the second state,rotation of the output shaft 224 causes the cam 108 to rotate and alower diameter surface to come in contact with the roller 112. In thisposition, the teeth 114 of the pawl 110 to remain separated from theparking gear such as not lodged within a ridge 116 of the parking gear.In this position, the pawl is not in contact with the parking gear 115,thereby allowing the parking gear 115 to rotate along with thetransmission system as engine torque is transmitted to the vehiclewheels via the output shaft of the transmission system. In the secondstate, the vehicle wheels are free to rotate.

FIG. 2A-C show schematics of an electronic actuation system 201 forengaging/disengaging a parking mechanism (such as parking mechanism 101in FIG. 1) of a vehicle transmission system. The electronic actuationsystem 201 may include a first parallel axis gear 206 coupled to amotor/pinion gear 204 of a drive motor 202. The drive motor (actuator)202 may be an electric motor such as a brushless motor, shunt motor,stepper motor, and other types of electric motors. The drive motor 202may be selectively operated to rotate the motor/pinion gear 204 in aclockwise (first) and an anticlockwise (second) direction.

The first parallel axis gear 206 may include a second attached parallelaxis gear 208 fixed to the center of the first parallel axis gear 206.The second parallel axis gear 208 may rotate at the same speed and inthe same direction as the first parallel axis gear 206. The secondparallel axis gear 208 may provide an interface between the firstparallel axis gear 206 and an adjacent final parallel axis gear 210. Thesecond parallel axis gear 208 may be in face sharing contact with aperimeter of the final parallel axis gear 210. In one example, thesecond parallel axis gear 208 and the perimeter of the final parallelaxis gear 210 may include complementary geometries such as teeth andgroves that allow effective coupling of the first parallel axis gear 206and the final parallel axis gear 210 via the second parallel axis gear208.

Each of the first parallel axis gear 208 and the final parallel axisgear 210 may be configured to rotate in both clockwise and anticlockwisedirections along their respective central axes. The central axis of thefirst parallel axis gear 208 may pass through the center of the secondparallel axis gear 208, and the central axis of the final parallel axisgear 210 may pass through the center 216 of the final parallel axis gear210.

A lever arm 218 may be coupled to the final parallel axis gear 210 via adrive pin 212 fixed to and eccentric to the final parallel axis gear210. The lever arm 218 may include an elongated slot 215 proximal to itsfirst end. In one example, a rolling element may be mounted on the drivepin 212 and the rolling element may be positioned within the slot 215 ofthe lever arm 218, thereby coupling the lever arm 218 to the finalparallel axis gear 210 via the drive pin 212. The slot 215 may beelongated along the longitudinal A-A′ axis of the lever arm 218 withrounded ends complementary to the radius of the drive pin 212 housedthere within. Each of the first parallel axis gear 206, the finalparallel axis gear 210, and the lever arm 218 may be substantiallycoplanar with the longitudinal A-A′ axis of the lever arm 218 making anangle to an axis connecting a center of the first parallel axis gear 206to the center of the final parallel axis gear 210.

The drive pin 212 may move along a length of slot 215 as the finalparallel axis gear 210 rotates about the center 216 of the finalparallel axis gear 210. The lever arm is free to rotate about drive pin212. During rotation of the final parallel axis gear 210, the drive pin212 may not align with the center 216 of the final parallel axis gear210 and the drive pin 212 may be off-centered relative to the center 216of the final axis gear 210.

A locking pin 222 may be coupled to the final parallel axis gear 210,off-centered, towards the perimeter of the final parallel axis gear 210.The locking pin 222 may protrude outward from and may be perpendicularto the plane of the final parallel axis gear 210 and rotate along withthe final parallel axis gear 210. In this embodiment, the locking pin222 is shown as a pin protruding out of the final parallel axis gear210, however, in other embodiments, the locking pin 222 may be replacedby any form of obstruction such as a bump at the position of the lockingpin 222 on the final parallel axis gear 210, or a tooth sticking out atthe position of the locking pin 222 on the final parallel axis gear 210.

During rotation of the final parallel axis gear 210 and the lever arm218, the locking pin 222 may provide an obstruction hindering furthermovement of the lever arm 218. Rotational degrees of freedom of thelever arm 218 may be lower than the rotational freedom of each of thefirst parallel axis gear 206 and the final parallel axis gear 210. Therotational freedom of the lever arm 218 may be limited by the lockingpin 222. The lever arm 218 may be locked at one of a first positioncorresponding to a first position of the locking pin 222 and at a secondposition corresponding to a second position of the locking pin 222. Assuch, once the lever arm 218 is rotated, in aclockwise/counter-clockwise direction, beyond a point (refereed hereinas tangent point) where the drive pin 212 travel is tangent to the axisA-A′ of the lever arm 218, any further force on the lever arm 218 may beself-locking, causing the lever arm to be locked in contact with thelocking pin 222. At the tangent point, rotation of the final parallelaxis gear 210 may not translate to any movement of the lever arm 218.

An output shaft 224 may be coupled to a second end of the lever arm 218,the second end distal from the first end and the slot 215. The outputshaft 224 may be perpendicular to the plane of the lever arm 218. Theshaft may be coupled to a pawl of a transmission system via a cam. Whenthe lever arm 218 is locked in the first position, the electronicactuation system 201 may be in a first state, and the output shaft 224may actuate the pawl to engage with a parking gear of the transmissionsystem corresponding to a first, engaged position of the parkingmechanism. In the first, engaged position of the parking mechanism, thetransmission system is on a park mode and the vehicle wheels may not berotated. When the lever arm 218 is locked in the second position, theelectronic actuation system 201 may be in a first state, and the outputshaft 224 may actuate the pawl to disengage from the parking gear of thetransmission system corresponding to a second, disengaged position ofthe parking mechanism. In the second, disengaged position of the parkingmechanism, the transmission system is not on a park mode and the vehiclewheels may be rotated.

A position sensor may be coupled to one or more components of theelectronic actuation system 201. In this example, a position sensor 225may be coupled to the final parallel axis gear 210 or the lever arm 218.During transition of the electronic actuation system 201 from a firstposition to a second position, the position sensor 225 may determine thecurrent position such as a distance of the lever arm, 218 from thelocking pin 222. The sensor 225 may be one of an inductive sensor and aHall Effect sensor.

FIG. 2A shows an example schematic 200 of the electronic actuationsystem 201 in a first state. In the first state, the lever arm 218 islocked in a first, position with the left edge of the lever arm 218 incontact with the locking pin 222. In order to reach the first, locked,position, of the lever arm 218, the final parallel axis gear 210 may berotated counterclockwise past the tangent point where the drive pin 212travel is tangent to the axis A-A′ of the lever arm 218. Due to therotation of the final parallel axis gear 210 beyond the tangent point, aclockwise torque on the lever arm 218 may result in a counterclockwisetorque on the final parallel axis gear 210.

The presence of the locking pin 222 inhibits further clockwise movement(towards left) of the lever arm 218. Once the lever arm 218 crosses thetangent point, even if an external force is applied to rotate the leverarm 218 in the counter-clockwise direction (towards right), the forcegenerated in the direction to back drive the lever arm 218 may not besufficient to rotate the lever arm 218 past the tangent point. In thisway, the lever arm 218 may be locked in a first position causing theactuation system and the attached parking mechanism to be non-backdrivable.

In response to the output shaft 224 being in the first position, a teethof a pawl of the transmission system may be inserted in a ridge betweenteeth of a parking gear, thereby causing the parking gear and the outputshaft of the transmission system to stop rotating. Since the electronicactuation system 201 is non-back drivable, the parking gear may remainstationary until the motor/pinion gear 204 of a drive motor 202 isactuated by the controller. In this way, when the vehicle is parked at aslope and the parking mechanism is engaged, the non-back drivableelectronic actuation system 201 may provide stability to the vehicle andinhibit undesired movement of the wheels. An operator/user may select apark mode of the transmission system via an instrument panel in thevehicle.

FIG. 2C shows an example schematic 260 of the electronic actuationsystem 201 in a second state. In the second state, the lever arm 218 islocked in a second, position with the right edge of the lever arm 218 incontact with the locking pin 222. In order to reach the second, locked,position, of the lever arm 218, the final parallel axis gear 210 may berotated clockwise past the tangent point where the drive pin 212 travelis tangent to the axis A-A′ of the lever arm 218.

The presence of the locking pin 222 inhibits further counter-clockwisemovement (towards right) of the lever arm 218. Once the lever arm 218crosses the tangent point, even if an external force is applied torotate the lever arm 218 in the clockwise direction (towards left), theforce generated in the direction to back drive the lever arm 218 may notbe sufficient to rotate the lever arm 218 past the tangent point. Inthis way, the lever arm 218 may be locked in a second position causingthe actuation system and the attached parking mechanism to be non-backdrivable.

In response to the output shaft 224 being in the second position, theteeth of the pawl of the transmission system may be disengaged from theparking gear, thereby causing the parking gear and the output shaft ofthe transmission system to be able to rotate. Since the electronicactuation system 201 is non-back drivable, the pawl may remaindisengaged until the motor/pinion gear 204 of a drive motor 202 isactuated by the controller. In this way, when the vehicle is operatingand the transmission system is not in the park mode, the non-backdrivable electronic actuation system 201 may inhibit undesired stoppingof the wheels. An operator may disengage the parking mechanism from anengaged position by selecting a mode of the transmission system otherthan park via an instrument panel in the vehicle.

FIG. 2B shows an example schematic 220 of the electronic actuationsystem 201 transitioning from the first state (as shown in FIG. 2A) tothe second state (as shown in FIG. 2C). In the first state of theelectronic actuation system 201, the lever arm 218 may be locked in afirst position and a parking mechanism may be engaged. In the secondstate of the electronic actuation system 201, the lever arm 218 may belocked in a second position and a parking mechanism may be disengaged.Engagement and disengagement of the parking mechanism may be initiatedby the vehicle operator by selecting a mode of operation of thetransmission system such as park, drive, reverse etc. via an on-boardinstrument panel. The motor/pinion gear 204 and the parallel axis geartrain may remain stationary when the electronic actuation system 201 iseither in the first state or the second state, and the motor/pinion gear204 and the parallel axis gear train may only rotate during thetransition of the electronic actuation system 201 from one state toanother.

In response to a command from the operator to disengage the parkingmechanism such as upon shifting the transmission system from park todrive, the electronic actuation system 201 may be transitioned from thefirst state to the second state. The motor/pinion gear 204 of the drivemotor 202 may be rotated in a clockwise direction causing each of thefirst parallel axis gear 206 and the second parallel axis gear 208 torotate in counter-clockwise directions about their respective axes. Thefinal parallel axis gear 210 may then rotate clockwise about its center216. Rotation of the final parallel axis gear 210 may cause the drivepin mounted on the final parallel axis gear 210 to rotate and slidewithin the slot 215 in the lever arm 218. The final parallel axis gear210 may be rotated clockwise past the tangent point where the drive pin212 travel is tangent to the axis A-A′ of the lever arm 218 causing thelever arm 218 to be rotated in the counter-clockwise direction until itmeets the locking pin 222. Once the lever arm 218 is in contact with thelocking pin 222, the lever arm 218 may be locked in the second position.

During transition of the electronic actuation system 201 from the firststate to the second state, a position of the parallel axis drive trainmay be monitored via the sensor 225. If it is determined that after athreshold duration has elapsed since the transition of the electronicactuation system 201 to the second state and yet the second state hasnot been reached, it may be inferred that the parallel axis train isstuck in between the first state and the second state, and a diagnosticscode may be set indicating degradation of the electronic actuationsystem 201. In this way, diagnostics of the electronic actuation system201 may be carried out during transition of the system from one non-backdrivable state to another.

FIG. 4 shows an example method 400 for operating an electronic actuationsystem (such as electronic actuation system 201 in FIGS. 2A-2C) of aparking mechanism (such as parking mechanism 101 in FIG. 1) of a vehicletransmission system. The parking mechanism may be actuated to engage apawl with a parking gear which would inhibit the vehicle wheels fromrolling, and disengage the pawl from the parking gear which would allowmovement of the vehicle wheels. Instructions for carrying out method 400and the rest of the methods included herein may be executed by acontroller based on instructions stored on a memory of the controllerand in conjunction with signals received from sensors of the vehiclesystem. The controller may employ engine actuators of the vehicle systemto adjust engine operation, according to the methods described below.

At 402, the routine includes determining if a park mode of thetransmission system has been selected. A vehicle operator may select amode of operation of the transmission system such as park via an onboardinstrument panel. When the park mode is selected, the controller mayactuate the parking mechanism to a first position to engage the pawl ofthe transmission system with the parking gear to inhibit further motionof the output shaft of the transmission system and the wheels.

If it is determined that park mode of the transmission system is notselected, at 416, the transmission system may be maintained in thecurrent mode. As an example, the parking mechanism may be continued in asecond position where the pawl is not engaged with the parking gear andthe output shaft of the transmission system and the wheels are able torotate.

If it is determined that the park mode is selected, at 404, amotor/pinion gear (such as motor/pinion gear 204 in FIGS. 2A-C) of adrive motor (such as drive motor 202 in FIGS. 2A-C) of the electronicactuation system may be rotated in a counter-clockwise direction. Thecontroller may send a signal to the actuator of the motor/pinion gear torotate the motor/pinion gear in the counter-clockwise direction.

At 406, counter-clockwise rotation of the motor/pinion gear may causethe first gear (such as first parallel axis gear 206 in FIGS. 2A-C) ofthe parallel axis gear train meshed with the motor/pinion gear to rotateclockwise. Rotation of the first gear may also cause a second gear (suchas second parallel axis gear 208 in FIGS. 2A-C) mounted at the center ofthe first gear to rotate in the clockwise direction.

At 408, an output gear (such as final parallel axis gear 210 in FIGS.2A-C) of the electronic actuation system meshed with the second gear mayrotate in a counter-clockwise direction about its axis. Rotation of theoutput gear may cause the lever arm fixed to and eccentric to the finalgear via a drive pin (such as drive pin 212 in FIG. 2A-C) to rotate. Asthe final gear rotates, the lever arm may rotate and slide along theslot housing the drive pin. At 410, the lever arm may be rotatedcounter-clockwise until the lever arm is locked in a first staticposition. In order to reach the first static position, the final gearmay be rotated in a counterclockwise direction past a tangent pointwhere the direction of travel of the drive pin is tangent to the axis ofthe lever arm until the lever arm is contacting a locking pin (such aslocking pin 222 in FIG. 222). Upon reaching the first, static position,the lever arm is non-back drivable even if external torque is applied onthe lever arm. At the first static state of the lever arm, an outputshaft coupled to the lever arm may actuate a cam to rotate and push downthe pawl to engage with a groove of the parking gear. Once a teeth ofthe pawl is lodged in a groove of the parking gear, the parking gear isstationary causing rotation of the output shaft of the transmissionsystem and the vehicle wheels to stop moving.

At 412, the routine includes determining if a first static state of thelever arm has been reached within a first threshold time from theselection of the parking mode (step 402). The first threshold time maybe pre-calibrated based on a time taken for the lever arm to travel froma second static state (corresponding to a disengaged parking gear) tothe first static state upon actuation of the motor. The position of theparallel axis gear train including the position of the lever arm may bemonitored by a sensor (such as a position sensor 225 in FIGS. 2A-C)coupled to either the final gear or the lever arm.

If it is determined that the first static state of the lever arm has notbeen reached within the first threshold time from the from the selectionof the parking mode, it may be inferred that the electronic actuationmechanism is stuck such as one or more gears of the parallel axis geartrain is stuck in an intermediate position while transitioning from thesecond to the first state. As such, the electronic actuation system maynot rest at any intermediate position between the first and secondstates and may only be locked in one of the first and the second state.At 414, degradation of the electronic actuation system may be indicatedby setting a flag (diagnostic code) and displaying a message in thevehicle dashboard. In response to degradation of the electronicactuation system of the parking mechanism, vehicle operations may beadjusted to mitigate the degradation. In one example, a backupelectronic parking brake may be applied to inhibit movement of thewheels when the transmission system is desired to be operated in a parkmode.

If at 412, it is determined that the first static state of the lever armhas been reached within the first threshold time from the selection ofthe parking mode, it may be inferred that the pawl has been engaged withthe parking gear and will be maintained in the engaged position until adifferent mode (other than park) of the transmission system is selected.

At 418, the routine includes determining if the transmission system modeis changed from park to any other transmission system mode such asdrive, reverse, etc. by the operator via the onboard instrument panel.When the transmission system mode is changed from the park mode, thecontroller may actuate the parking mechanism to a second position todisengage the pawl of the transmission system from the parking gear toenable motion of the output shaft of the transmission system and thewheels.

If it is determined that a change in transmission mode from park has notbeing indicated, at 420, the transmission system mode is maintained inthe park mode. As an example, the parking mechanism may be continued ina first position where the pawl is engaged with the parking gear and theoutput shaft of the transmission system and the wheels are unable torotate.

If the transmission system mode is changed, at 422, the motor/piniongear of the drive motor of the electronic actuation system may berotated in a clockwise direction. The controller may send a signal tothe actuator of the motor/pinion gear to rotate the motor/pinion gear inthe clockwise direction.

At 424, clockwise rotation of the motor/pinion gear may cause the firstgear of the parallel axis gear train meshed with the motor/pinion gearto rotate counter-clockwise. Rotation of the first gear may also causethe second gear mounted at the center of the first gear to also rotatein the counter-clockwise direction.

At 426, the output gear of the electronic actuation system meshed withthe second gear may rotate in a clockwise direction about its axis.Rotation of the output gear may cause the lever arm fixed to andeccentric to the final gear via a drive pin to rotate. As the final gearrotates, the lever arm may rotate and slide along the slot housing thedrive pin. At 428, the lever arm may be rotated clockwise until thelever arm is locked in a second static position. In order to reach thesecond static position, the final gear may be rotated in a clockwisedirection past a tangent point where the direction of travel of thedrive pin is tangent to the axis of the lever arm until the lever arm iscontacting the locking pin. Upon reaching the second, static position,the lever arm is non-back drivable even if external torque is applied onthe lever arm. At the second static state of the lever arm, an outputshaft coupled to the lever arm may actuate a cam to rotate and releasethe pawl from engagement with a groove of the parking gear. Once a teethof the pawl is dislodged from the groove of the parking gear, theparking gear is able to rotate causing the output shaft of thetransmission system and the vehicle wheels to rotate.

At 430, the routine includes determining if a second static state of thelever arm has been reached within a second threshold time from thechange in transmission mode (step 418). The second threshold time may bepre-calibrated based on a time taken for the lever arm to travel from afirst static state to the second static state. In one example, the firstthreshold time and the second threshold time may be equal. In oneexample, the first threshold time and the second threshold time may beunequal. The position of the parallel axis gear train including theposition of the lever arm may be monitored by the position sensorcoupled to either the final gear or the lever arm.

If it is determined that the second static state of the lever arm hasnot been reached within the second threshold time from the change intransmission mode, it may be inferred that the electronic actuationmechanism is stuck such as one or more gears of the parallel axis geartrain is stuck in an intermediate position while transitioning from thefirst to the second state and the routine may proceed to step 414 toindicate degradation of the electronic actuation system. If it isdetermined that the second static state of the lever arm has not beenreached within the second threshold time from the change in transmissionmode, at 432, the transmission system may be maintained in its currentmode with the pawl disengaged from the parking gear until further changein the transmission system.

In this way, during a first condition, a level arm coupled to a motorvia a parallel axis gear train may be rotated in a first direction untilan output gear of the parallel axis gear train is driven past a tangentpoint and is non-back drivable from a first state of the actuationsystem, and during a second condition, the level arm coupled to themotor via the parallel axis gear train may be rotated in a seconddirection until the output gear is driven past the tangent point and isnon-back drivable from a second state of the actuation system, thesecond direction opposite to the first direction. The first conditionmay include a park mode of the transmission system being selectedhindering movement of wheels of the vehicle, and the second conditionmay include another mode of the transmission system different from thepark mode being selected allowing movement of the wheels.

In one example, a actuation system in a parking mechanism of a vehicle,comprising: an actuator coupled to a lever arm via one or more gears,and an output shaft connecting the lever arm to a shifting member of theparking mechanism, the lever arm non-back drivable at each of a firststate and a second state of the actuation system. In the precedingexample, additionally or optionally, the first state of the actuationsystem corresponds to a pawl of a transmission system to be engaged to aparking gear hindering movement of wheels of the vehicle, and whereinthe second state of the actuation system corresponds to the pawl beingdisengaged from the parking gear allowing movement of the wheels. In anyor all of the preceding examples, additionally or optionally, the pawlis engaged to the parking gear upon selection of a park mode of thetransmission system by an operator of the vehicle via an instrumentpanel in the vehicle, and wherein the pawl is disengaged from theparking gear upon selection of a mode transmission system different fromthe park mode by the operator via the instrument panel. In any or all ofthe preceding examples, additionally or optionally, the one or moregears include a first parallel axis gear, a second parallel axis gear,and a final parallel axis gear coupled to a first end of the lever armvia an eccentric drive pin. In any or all of the preceding examples, thesystem further comprising, additionally or optionally, a locking pincoupled to the final parallel axis gear in face sharing contact with alever arm at each of the first state and the second state of theactuation system, the lever arm driven via the eccentric drive pinhoused within a slot in the lever arm. In any or all of the precedingexamples, additionally or optionally, the actuator is an electric motorcoupled to the first parallel axis gear. In any or all of the precedingexamples, additionally or optionally, the first parallel axis gear iscoupled to the final parallel axis gear via the second parallel axisgear and wherein the second parallel axis gear is fixed to a center ofthe first parallel axis gear, the second parallel axis gear in facesharing contact with a perimeter of the final parallel axis gear. In anyor all of the preceding examples, additionally or optionally, each ofthe first parallel axis gear, the final parallel axis gear, and thelever arm are coplanar with a longitudinal axis of the lever arm makingan angle to an axis connecting a center of the first parallel axis gearto the center of the final parallel axis gear and wherein the shaft iscoupled to a second end of the lever arm, the first end distal from thesecond end, the shaft perpendicular to a plane of the lever arm. In anyor all of the preceding examples, additionally or optionally, theshifting member of the parking mechanism is the pawl, the output shaftcoupled to the pawl via a cam and a roller. In any or all of thepreceding examples, additionally or optionally, in the first state ofthe actuation system, the cam pushes down the pawl via the roller toengage the pawl within a grove of the parking gear, and wherein thesecond state of the actuation system, the pawl is released from thegrove of the parking gear. In any or all of the preceding examples,additionally or optionally, the actuator rotating in a first directionrotates the first parallel axis gear in a second direction and the finalparallel axis gear in the first direction past a tangent point until thelever arm is in face sharing contact with the locking pin locking theactuation system in the first state and wherein the actuator rotating inthe second direction rotates the first parallel axis gear in the firstdirection and the final parallel axis gear in the second direction pastthe tangent point until the lever arm is in face sharing contact withthe locking pin locking the actuation system in the second state, thefirst direction opposite to the second direction.

In another example, a method for an actuation system, comprises: duringa first condition, rotating a level arm coupled to a motor via aparallel axis gear train in a first direction until an output gear ofthe parallel axis gear train is driven past a tangent point and isnon-back drivable from a first state of the actuation system, and duringa second condition, rotating the level arm coupled to the motor via theparallel axis gear train in a second direction until the output gear isdriven past the tangent point and is non-back drivable from a secondstate of the actuation system, the second direction opposite to thefirst direction. In the preceding example, additionally or optionally,the lever arm is coupled to the output gear of the parallel axis geartrain via a drive pin housed within a slot in the lever arm, and at thetangent point, a direction of travel of the drive pin is tangential to alongitudinal axis of the lever arm, and wherein the lever arm is furthercoupled to a pawl of a transmission system of a vehicle via a cam. Inany or all of the preceding examples, additionally or optionally, thefirst condition includes a park mode of the transmission system beingselected hindering movement of wheels of the vehicle and the secondcondition includes another mode of the transmission system differentfrom the park mode being selected allowing movement of the wheels. Inany or all of the preceding examples, additionally or optionally, whenthe park mode is selected, the pawl engages with a parking gear of thetransmission system suspending movement of the parking gear. In any orall of the preceding examples, additionally or optionally, the actuationmechanism transitions from the first state to the second state uponchange in the transmission mode from the park mode to another mode andwherein the actuation mechanism transitions from the second state to thefirst state upon selection of the park mode. In any or all of thepreceding examples, the method further comprising, additionally oroptionally, during transitioning from the second state to the firststate, estimating a position of the parallel axis gear train via aposition sensor coupled to the parallel axis gear train, and in responseto the first state not being reached within a first threshold duration,indicating degradation of the actuation system, and during transitioningfrom the first state to the second state, estimating the position of theparallel axis gear train via the position sensor, and in response to thesecond state not being reached within a second threshold duration,indicating degradation of the actuation system.

In yet another example, method for a transmission system of a vehicle,comprises: rotating a parallel axis gear coupled to a lever arm througha drive pin in a slot of the lever arm, the drive pin fixed to theparallel axis gear, to rotate the lever arm, and engaging anddisengaging a pawl of the transmission system by the rotation of thelever arm between two fixed end positions, rotational degrees of thelever arm substantially less than rotational degrees of the parallelaxis gear. In the preceding example, additionally or optionally, uponselection of a park mode of the transmission system, the lever arm isrotated counter-clockwise from a second end position until a first endposition is reached, the first end position corresponding to the pawlbeing engaged. In any or all of the preceding examples, additionally oroptionally, upon indication of selection of another mode of thetransmission system different from the park mode, the lever arm isrotated clockwise from the first end position until the second endposition is reached, the second end position corresponding to the pawlbeing disengaged.

FIGS. 1-2A, B, C show example configurations with relative positioningof the various components. If shown directly contacting each other, ordirectly coupled, then such elements may be referred to as directlycontacting or directly coupled, respectively, at least in one example.Similarly, elements shown contiguous or adjacent to one another may becontiguous or adjacent to each other, respectively, at least in oneexample. As an example, components laying in face-sharing contact witheach other may be referred to as in face-sharing contact. As anotherexample, elements positioned apart from each other with only a spacethere-between and no other components may be referred to as such, in atleast one example. As yet another example, elements shown above/belowone another, at opposite sides to one another, or to the left/right ofone another may be referred to as such, relative to one another.Further, as shown in the figures, a topmost element or point of elementmay be referred to as a “top” of the component and a bottommost elementor point of the element may be referred to as a “bottom” of thecomponent, in at least one example. As used herein, top/bottom,upper/lower, above/below, may be relative to a vertical axis of thefigures and used to describe positioning of elements of the figuresrelative to one another. As such, elements shown above other elementsare positioned vertically above the other elements, in one example. Asyet another example, shapes of the elements depicted within the figuresmay be referred to as having those shapes (e.g., such as being circular,straight, planar, curved, rounded, chamfered, angled, or the like).Further, elements shown intersecting one another may be referred to asintersecting elements or intersecting one another, in at least oneexample. Further still, an element shown within another element or shownoutside of another element may be referred as such, in one example.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. An actuation system in a parking mechanism of a vehicle, comprising:an actuator coupled to a lever arm via one or more gears; and an outputshaft connecting the lever arm to a shifting member of the parkingmechanism, the lever arm non-back drivable at each of a first state anda second state of the actuation system; wherein a first end of the leverarm is coupled to a final parallel axis gear of the one or more gearsvia an eccentric drive pin housed within a slot in the lever arm,wherein the lever arm is driven solely via the eccentric drive pin, thelever arm not directly attached to the one or more gears, wherein afirst parallel axis gear of the one or more gears is coupled to thefinal parallel axis gear via a second parallel axis gear, and whereinthe second parallel axis gear is fixed to a center of the first parallelaxis gear.
 2. The system of claim 1, wherein the first state of theactuation system corresponds to a pawl of a transmission system to beengaged to a parking gear hindering movement of wheels of the vehicle,and wherein the second state of the actuation system corresponds to thepawl being disengaged from the parking gear allowing movement of thewheels.
 3. The system of claim 2, wherein the pawl is engaged to theparking gear upon selection of a park mode of the transmission system byan operator of the vehicle via an instrument panel in the vehicle, andwherein the pawl is disengaged from the parking gear upon selection of amode transmission system different from the park mode by the operatorvia the instrument panel.
 4. The system of claim 1, wherein the one ormore gears include the first parallel axis gear, the second parallelaxis gear, and the final parallel axis gear coupled to the first end ofthe lever arm.
 5. The system of claim 4, further comprising, a lockingpin coupled to the final parallel axis gear in face sharing contact withthe lever arm at each of the first state and the second state of theactuation system.
 6. The system of claim 4, wherein the actuator is anelectric motor coupled to the first parallel axis gear.
 7. The system ofclaim 4, wherein the second parallel axis gear is in face sharingcontact with a perimeter of the final parallel axis gear.
 8. The systemof claim 4, wherein a longitudinal axis of the lever arm makes an angleto an axis connecting the center of the first parallel axis gear to thecenter of the final parallel axis gear and wherein the shaft is coupledto a second end of the lever arm, the first end of the lever arm distalfrom the second end of the lever arm, and the shaft perpendicular to aplane of the lever arm.
 9. The system of claim 2, wherein the shiftingmember of the parking mechanism is the pawl, the output shaft coupled tothe pawl via a cam and a roller.
 10. The system of claim 9, wherein inthe first state of the actuation system, the cam pushes down the pawlvia the roller to engage the pawl within a grove of the parking gear,and wherein the second state of the actuation system, the pawl isreleased from the grove of the parking gear.
 11. The system of claim 5,wherein the actuator rotating in a first direction rotates the firstparallel axis gear in a second direction and the final parallel axisgear in the first direction past a tangent point until the lever arm isin face sharing contact with the locking pin locking the actuationsystem in the first state and wherein the actuator rotating in thesecond direction rotates the first parallel axis gear in the firstdirection and the final parallel axis gear in the second direction pastthe tangent point until the lever arm is in face sharing contact withthe locking pin locking the actuation system in the second state, thefirst direction opposite to the second direction.
 12. A method for anactuation system, comprising: during a first condition, rotating a leverarm coupled to a motor via a parallel axis gear train in a firstdirection until an output gear of the parallel axis gear train is drivenpast a tangent point and is non-back drivable from a first state of theactuation system, and a locking pin coupled to a final parallel axisgear of the parallel axis gear train is in face sharing contact with thelever arm; and during a second condition, rotating the lever arm coupledto the motor via the parallel axis gear train in a second directionuntil the output gear is driven past the tangent point and is non-backdrivable from a second state of the actuation system, and the lockingpin is in face sharing contact with the lever arm, the second directionopposite to the first direction, wherein the lever arm is coupled to theoutput gear of the parallel axis gear train via a drive pin housedwithin a slot in the lever arm, and at the tangent point, a direction oftravel of the drive pin is tangential to a longitudinal axis of thelever arm, and wherein the lever arm is further coupled to a pawl of atransmission system of a vehicle via a cam.
 13. (canceled)
 14. Themethod of claim 12, wherein the first condition includes a park mode ofthe transmission system being selected hindering movement of wheels ofthe vehicle and, wherein the second condition includes another mode ofthe transmission system different from the park mode being selectedallowing movement of the wheels.
 15. The method of claim 14, whereinwhen the park mode is selected, the pawl engages with a parking gear ofthe transmission system suspending movement of the parking gear.
 16. Themethod of claim 14, wherein the actuation system transitions from thefirst state to the second state upon change in the transmission systemfrom the park mode to another mode and wherein the actuation systemtransitions from the second state to the first state upon selection ofthe park mode.
 17. The method of claim 12, further comprising, duringtransitioning from the second state to the first state, estimating aposition of the parallel axis gear train via a position sensor coupledto the parallel axis gear train, and in response to the first state notbeing reached within a first threshold duration, indicating degradationof the actuation system, and during transitioning from the first stateto the second state, estimating the position of the parallel axis geartrain via the position sensor, and in response to the second state notbeing reached within a second threshold duration, indicating degradationof the actuation system.
 18. A method for a transmission system of avehicle, comprising: rotating a parallel axis gear coupled to a leverarm through an eccentric drive pin housed in a slot of the lever arm,the drive pin fixed to the parallel axis gear to rotate the lever armand the lever arm not directly attached to the parallel axis gear; andengaging and disengaging a pawl of the transmission system by therotation of the lever arm between two fixed end positions, wherein thelever arm rotates through an angle substantially smaller than an angleof rotation of the parallel axis gear, and wherein at the two fixed endpositions, a locking pin coupled to a final parallel axis gear of theparallel axis gear is in face sharing contact with the lever arm. 19.The method of claim 18, wherein upon selection of a park mode of thetransmission system, the lever arm is rotated counter-clockwise from asecond end position until a first end position is reached, the first endposition corresponding to the pawl being engaged.
 20. The method ofclaim 19, wherein upon indication of selection of another mode of thetransmission system different from the park mode, the lever arm isrotated clockwise from the first end position until the second endposition is reached, the second end position corresponding to the pawlbeing disengaged.